Heavy people with type 2 diabetes who lose a modest amount of weight and keep it off get many long-term health benefits such as reducing their risk of chronic kidney disease, depression and eye disease, according to the latest findings of a landmark study.

They also have better blood sugar control, improved quality of life and fewer hospitalizations, and they take less medication, thus reducing medical costs.

But the weight loss doesn't lower their risk of having a heart attack or stroke. The study's authors reported that information last fall.

"Weight loss is still important, but the reasons why it is important are different than we thought," says Rena Wing, a professor of psychiatry and human behavior at Brown University and chairman of the Look AHEAD (Action for Health in Diabetes) study.

The study was designed to see whether weight loss reduced the risk of heart attacks and strokes. Wing and other investigators presented their findings Monday at the American Diabetes Association's annual scientific meeting in Chicago.

"Other short-term studies have shown the benefits of weight loss (for people with diabetes), but this is the first large, long-term trial examining a diverse set of health benefits," says Tim Church, director of preventive medicine research at the Pennington Biomedical Research Center in Baton Rouge.

Almost 26 million children and adults in the USA (8.3% of the population) have diabetes. There are two major forms: type 1 and type 2, which accounts for 90% to 95% of cases. In people with diabetes, the body does not make enough of the hormone insulin or doesn't use it properly. Insulin helps glucose (sugar) get into cells, where it is used for energy. If there's an insulin problem, sugar builds up in the blood, damaging nerves and blood vessels.

Diabetes can lead to heart disease, stroke, kidney failure, foot and leg amputations and blindness.

For the study, researchers at 16 centers around the country worked with 5,145 obese people with type 2 diabetes. Their average starting weight was about 200 pounds.

Half of the participants were assigned to an intensive diet and exercise program. They attended individual and group meetings where they were taught strategies for weight loss by cutting calories and increasing physical activity. They used some meal replacements during the weight-loss and maintenance phases of the program.

The other half received a general program of diabetes education and support several times a year. All participants continued to follow the medical advice of their physicians. Participants were followed for about 10 years. Among findings:

-- Those in the diet-and-exercise group lost about 8.6% of their starting weight in the first year and maintained a 6% loss after about 10 years. Participants in the diabetes education group lost almost 1% of their starting weight at one year, and at 10 years they had lost about 3.5%.

-- Participants in the diet-and-exercise group were 31% less likely to develop chronic kidney disease than the diabetes education group.

-- The diet-and-exercise group improved their hemoglobin A1C readings (which looks at a person's average blood sugar levels for the past three months) and HDL (so-called good cholesterol) more than those in the diabetes education group. The diet-and-exercise group also required less medication to control the diabetes, Wing says.

-- Participants in the diabetes education group, however, had better LDL (bad cholesterol) during the study, possibly because more of them were taking cholesterol-lowering statin medications, she says.

There was no difference between the two groups in the incidence of heart attacks and strokes, but the incidence was low in both groups, Wing says. The lower rates of cardiovascular disease may reflect improvements in the medical management of patients' diabetes, she says.

Researchers will continue to monitor the study participants to assess other possible long-term benefits of weight loss, Wing adds.

Church says the low rates of cardiovascular disease in study participants, especially the diabetes education group, "reflect the growing national trend of doctors aggressively treating chronic conditions such as high cholesterol and hypertension."

Gary Foster, director of the Center for Obesity Research and Education at Temple University in Philadelphia, says the study shows that weight loss gives people with a diabetes "a pretty big bang for their buck. It looks like there are whopping effects on kidney disease."

He says the other impressive result is that the people who lost weight were able to keep most of it off, contrary to the popular wisdom that just about everyone who loses weight regains it.

The research was financed primarily by the National Institute of Diabetes and Digestive and Kidney Disease, part of the National Institutes of Health.

Risk factors for diabetes:

People with the following risk factors are more likely to develop prediabetes and type 2 diabetes, according to the Centers for Disease Control and Prevention:

-- Age 45 or older

-- Overweight

-- Have a parent with diabetes

-- Have a sister or brother with diabetes

-- Family background is African American, Hispanic/Latino, American Indian, Asian American or Pacific Islander

-- Developed diabetes while pregnant (gestational diabetes) or gave birth to a baby weighing 9 pounds or more